1. Field of the Invention
The present invention relates to a pixel information management apparatus and an image capture apparatus using the same. In particular, the present invention relates to a technique of efficiently managing information about pixels included in an image sensor (pixel information), and a technique for processing signals using the pixel information.
2. Description of the Related Art
Conventionally, image sensors have been proposed that are capable of acquiring both phase-difference-detection-type focus detection signals and image capture signals, by forming some of the pixels as pupil-divided focus detection pixels. Focus detection pixels are special pixels having a partial light-shielding layer between a microlens and a photoelectric conversion unit. It is possible to form focus detection pixels whose pupil region where the photoelectric conversion unit receives light is different by changing the layout of the light-shielding layer, and to detect the amount and direction of defocus based on the shift amount and the shift direction in a pair of image signals (also referred to as “A image” and “B image”) formed based on the outputs of the same type of focus detection pixels.
With such an image sensor, it is necessary to distinguish whether a pixel signal output from the image sensor is the output of a focus detection pixel or the output of an imaging pixel to process the signals. Specifically, it is necessary to form an image signal for focus detection with regard to the output of a focus detection pixel, and to interpolate an image capture signal for the position of the focus detection pixel with regard to the output of an imaging pixel. It is possible to distinguish between the output of focus detection pixels and the output of imaging pixels by storing the positions of the focus detection pixels in a non-volatile memory in advance.
Note that it is conventionally known that the position of a defective pixel included in the image sensor is stored in advance and an image capture signal for the position of the defective pixel is interpolated. Since image capture signals for the position of the focus detection pixel can be similarly interpolated, it is not necessary to change the method for processing signals even in the case where an image sensor having focus detection pixels is used, as long as information on the position of the focus detection pixels as well as the position of the defective pixels is stored.
Meanwhile, there have been various proposals since focus detection accuracy is influenced by how the focus detection pixels are laid out or what type of focus detection pixels are laid out.
For example, Japanese Patent Laid-Open No. 2009-217074 discloses a technique for improving focus detection performance by using focus detection pixels that have different pupil division directions and devising a method for laying out the focus detection pixels.
Also, Japanese Patent Laid-Open No. 2010-113162 discloses that, even in the case where the center of the optical axis of the microlens shifts due to manufacturing error, good focus detection accuracy is realized by laying out, in the image sensor, focus detection pixels that have five types of openings, with the center of a pupil for performing pupil division being shifted slightly to the left or right.
In the case where a configuration including all the different types of openings disclosed in Japanese Patent Laid-Open No. 2009-217074 and Japanese Patent Laid-Open No. 2010-113162 is adopted, there are five types of opening positions for each of four directions (i.e. vertical, horizontal, and two diagonal directions), and a further two types of opening positions for the shift direction are also required in order to generate a pair of image signals (A image and B image). As a result, 4 directions×5 opening positions×2 shift directions of the opening positions (for A image and B image), i.e. 40 types of the focus detection pixels in total are dispersedly laid out.
In this way, in the case where there are various types of focus detection pixels, the amount of information that needs to be stored in advance will increase because it is necessary to process output signals according to type. For example, Japanese Patent Laid-Open No. 2009-163229 discloses that correction information is stored that includes pixel addresses, which is information indicating the position of pixels for performing correction, pupil division direction bits, AB bits, focus detection pixel bits, and defect bits. Both information on defective pixels and information on focus detection pixels are stored in the correction information by using the focus detection pixel bits and the defect bits.
Also, the issue of how to store the pixel information in advance is not limited to focus detection pixels, and similar issues are conceivable for the pixel information of an image sensor having pixels other than imaging pixels.